UV/IR
Detector, which makes use of an ultraviolet radiation sensitive phototube in
addition to an infrared detector. This combination provides a flame detector
which is highly immune to false alarms. The UV portion of the detector, as
described in the previous section, is combined with an infrared detector, which
responds to changes in the intensity of infrared radiation. By sensing very
specific wavelengths in both the UV and IR spectra and then processing these Signals
with a microcomputer, a very high degree of discrimination is achieved. Incorporated
in the IR circuitry is a flicker discrimination circuit. This permits the
detector to ignore steady IR sources such as hot objects. The inherent
flickering of a flame provides the necessary modulation to activate the IR
circuit. Since
a flame is a copious source of both ultraviolet and infrared radiation,
discrimination is provided when both UV and IR emissions are detected. If only
UV is detected, as in the case of arc welding, no alarm is given. If only IR is
detected, such as a large modulating hot object, no alarm is given. However, if
both conditions are met in the correct combination and intensity, as determined
by an algorithm in the microcomputer, a fire is identified and the alarm
outputs are activated.
Current Level Detector
status
0mA Fault
2mA Optical
Integrity (io) Fault.
4mA Normal
Operation
8mA IR
Alarm Only
12mA UV
Alarm Only
16mA Pre-Fire
Alarm
20mA Fire
Alarm
No comments:
Post a Comment